The present invention relates to discharge means comprising a liquid conduit for discharging liquid from a container, at least one mouth through which liquid to be discharged can pass into the conduit, level follower means to ensure that the mouth is moved to follow the level of the liquid in the container as that level changes, and relative mouth-level adjustment means to adjust the level of the mouth between a position in which it is below the surface of liquid in a container to a position in which it is above that surface. If the liquid is effluent, this reduces the likelihood of ingress of untreated effluent filling the discharge pipe whilst the treatment of the effluent is in progress. When the mouth is below the level of effluent, it is just below the surface, to be clear of floating debris actually on the surface, to reduce the likelihood of such debris contaminating the clear treated effluent just below the surface. Such previously proposed discharge means have relative mouth-level adjustment means in the form of a cable and winch arrangement to raise and lower the mouth, but such means are cumbersome and difficult to install and maintain.
The present invention seeks to provide a remedy.
Accordingly, the present invention is directed to discharge means having the construction set out in the opening paragraph of the present specification, in which the relative mouth-level adjustment means comprise at least one float having a selectively variable displacement.
Such discharge means are especially effective within a container which constitutes an effluent treatment tank, and in which the liquid to be discharged by the discharge means is treated effluent. The or each float may be provided with means to pump air or other gaseous material into and out of the float. For example, the float may comprise a hollow body with an opening, such as a hollow cylinder closed at one end and open at the other. Such a float may be oriented such that its opening is directed downwardly, and the feed means may be arranged to feed air or other gaseous material into the interior of the float.
The conduit may comprise an arm which extends within the container interior from a position in the wall of the container which is below an intended level of the liquid, so that discharge can be effected by the Force of gravity. The arm may be pivoted to enable it to remain adjacent to the surface of liquid within a container whilst the level of that surface changes.